• Aphid feeding can cause stunted growth with curled or distorted leaves
• White cast skins of aphids can accumulate on the upper surface of leaves; they drop down from the leaves above
• Glasshouse mealybug is usually first noticed as a fluffy white wax, the insects or their orange-pink eggs can be found underneath this substance
• Some scale insects deposit their eggs under a covering of white waxy fibres
• Discoloured leaves Thrips feeding results in leaves becoming increasingly dull or silvery in appearance. Leaves with red spider mite damage show a fine pale mottling on the upper leaf surface.
• Sticky leaves With aphids, scale insects and mealybugs excess sugars are excreted as a sticky substance called honeydew. This lands on the leaves and stems were it is often colonised by sooty moulds, giving surfaces a blackened appearance. Thrips excrement spots look like small dollops of dark varnish
• Webbing A fine silk webbing may be seen on  plants with red spider mite

• Inspect new purchases; insects are often first brought into the home or glasshouse on new plants. This is especially true of mealybugs and scale insects where the adult females do not fly or crawl far
• Quarantine new plants where possible in order to give eggs and nymphs a chance to develop and be recognised, this may also give any populations time to develop and enable you to spot them without risk of them spreading to your other plants
• Monitor house plants frequently so that action can be taken before damaging populations develop
• Relocate plants that are tolerant of outdoor UK conditions, moving them outside can often yield an improvement in their condition as the sap feeding insects are then accessible to natural predators or cooler outdoor conditions can slow down their life cycles
• Separate plants with populations of sap feeding invertebrates from other unaffected houseplants to minimise spread within your collection
• Tolerate populations of sap feeding invertebrates where possible. Plants can tolerate some levels of mealybug, although populations can quickly build if left unchecked
• Replace plants heavily affected by scale or mealybugs; it can be simpler to dispose of heavily affected plants rather than try to eliminate mealybugs 
• Remove severely affected plants. Consider removing plants supporting large populations of spider mites from glasshouses, especially in late summer before lower temperatures and shorter days induce the females to seek sheltered places where they will remain dormant for the winter period
• Reduce unwanted plants in the glasshouse as this can reduce the number of host plants helping you to control populations, especially of glasshouse whitefly
• Increase ventilation, where sap feeding insects are present, this will help to check the growth of sooty moulds
• Increase humidity, by regularly spraying plants with water. This will help move conditions away from those that favour glasshouse red spider mites, though this will not on its own control the mite. Plants grown at high temperatures in dry, overcrowded glasshouses are more liable to damaging populations of red spider mites
• Clear out plant debris, whether you have house plants, plants in a conservatory or plants in a glasshouse, dead leaves and other plant material can harbour sap sucking insects
• Cleaning glasshouses in winter can help reduce overwintering populations. Empty glasshouses can be cleaned thoroughly with a glasshouse disinfectant
• Weeding in and around the glasshouse can be kept in check as these may act as hosts for glasshouse red spider mite
• Manual removal is feasible for some sap feeding invertebrates. You can use fingers and thumbs to squash aphid colonies. Adult scales can be removed when seen but this may not reduce large populations. It can be difficult to remove red spider mites due to their size, mealybugs due to the locations in which they are most often found, whitefly adults and thrips due to their mobility

• Sticky traps are not recommended out of doors as they often capture a large number of non-target invertebrates. In glasshouses they are still likely to catch non-target organisms including parasitoid wasp predators, that are released as biocontrol agents, so their use should be considered carefully. Inside the home they are less likely to catch other insects though they may not be considered visually attractive
• Hang sticky yellow sheets (widely available from garden suppliers) above or among plants in greenhouses to trap adult whitefly, this can help monitor whitefly activity rather than give control
• Hanging blue sticky traps (widely available from garden suppliers) above or among plants in glasshouses can trap thrips and help monitor and reduce numbers

Biocontrols
There are now biological controls available, from numerous suppliers, for all of these sap sucking invertebrates. They are most suitable for application in a glasshouse situation. All the biological controls are susceptible to pesticides and so cannot be used in conjunction with most pesticidal controls. 

• Organic sprays, such as natural pyrethrum or plant oils have a largely physical mode of action. These are broad spectrum so will kill a wide range of insects (including whitefly, thrips, scale insects, aphids and mealybug) and can give some control of glasshouse red spider mite. These pesticides have a very short persistence and so may require reapplication to keep numbers in check. Insects hidden in distorted leaves may be unaffected by these products. Plant oil and fatty acid products are less likely to affect larger insects like ladybirds
• Plant invigorators combine nutrients to stimulate plant growth with surfactants or fatty acids that have a physical mode of action. These products contain some synthetic ingredients and so are not considered organic
• Glasshouse fumigants can be used in glasshouses. Glasshouse should be sealed and instructions on the product label must be followed. An organic fumigant based on garlic is available and can be used when crop plants are present. Products based on the synthetic pyrethroid permethrin are available
• Contact action insecticides include the synthetic pyrethroids lambda-cyhalothrin, deltamethrin and cypermethrin are more persistant. Products containing these active ingredients have long lasting action against insects including those that are beneficial
• Systemic pesticides, those with both systemic (absorbed and transported through plant tissues) and contact action, are available. These include Flupyradifurone, for use against insects on ornamentals and selected edibles, and the neonicotinoid insecticide acetamiprid which is the active ingredient in products labelled for insects and red spider mite. These pesticides are widely considered to be the most environmentally damaging, remain active for a long time and will kill beneficial invertebrates

• With grape vines in glasshouses, peel away the loose outer bark to expose the scales before treatment
• Sprays used against scale insects are most likely to affect the young (nymphal) stage, for some scales they are only present at certain times of year, however the scale insects most likely to be found indoors breed all year round
• Dead scales can remain firmly attached to the plants. The success of any treatment can be gauged by the extent to which new growth remains free of scale insects
• Due partly to the waxy covering mealybugs are difficult to control with insecticides, affected plants will need to be sprayed thoroughly. In many cases it may be impossible to eliminate mealybugs
• Leaves affected by thrips will not regain their green colour, once it has been lost, even if the insect is no-longer present